How Long can a Generator Run

by Matthew Wilson

Last updated on July 4th, 2020

Last updated on July 4th, 2020

Most people welcome the peace of mind that comes from using a generator during a power outage or another situation that requires immediate power. A problem many people face is not knowing how long can a generator run before something terrible happens.

The question about how long a generator can, or should, run without maintenance is what we’re discussing here. The assumption seems that generators run continuously and won’t need maintenance, at least not for a long time. Too often, the inevitable happens, and the generator is disabled because of overheating and might require extensive repair.

That is a worst-case scenario that doesn’t need to happen – ever.

How Long Can a Portable Gas Generator Run?

Many circumstances require on-demand power for short periods. In contrast, others see the need for uninterrupted power for extended periods. Generators for camping trips or keeping your refrigerator running are a few of the typical uses.

A gas-powered generator has a limited continuous runtime based on the manufacturer’s specifications. Generators produce much heat, and when it’s time to refuel, it’s hazardous to pour gas into an empty tank while it’s hot and running.

how long can a generator run

Sparks from the tank can suddenly ignite fumes and start an uncontrollable fire.

The proper way to refuel is to shut down the generator and allow it to cool. Refer to the manufacturer’s instructions for safety and guidance.

Runtimes for gas portables can vary widely, but it depends on the tank capacity that could allow up to 18 hours of continuous runtime, and a few models extend that out to days.

Generators are mechanical wonders that require regular maintenance after a certain number of hours of continuous operation. By neglecting the care they need, generator assemblies will suffer dire yet preventable consequences.

Overnight Operation

Running your generator overnight is doable as long as the gas can last for at least eight hours. Fortunately, standard units run about eight hours per tank.

If your generator is noisy, you may have a discussion or two with your neighbors, so prepare for that. Leaving a running generator outside presents its own set of problems having to do with theft. Still, you can deal with that by enclosing the unit inside of a fenced-in area.

Propane Generators

For some, it’s an easy decision between using gas or propane units. Most lean toward propane for the convenience of hooking up to an LP tank and start generating electricity. For those times when power needs are immediate, propane is a natural choice. One obvious problem with propane is keeping the unit running continuously, considering its fuel usage.

You can easily accomplish the continuous operation of a propane-fueled generator by hooking up two tanks to a single gas line using a stopcock valve. That setup allows you to disconnect one empty tank and reconnect to a full one by opening or closing the stopcock valve.

The ease of a never-ending fuel supply has its downsides. When trying to determine how long will a generator run on propane, the fuel supply is only part of the equation.

Maintenance Requirements

Typical maintenance for a portable generator is once every 100 hours. Common sense and knowledge of your system are most important. Engine oil limitations set the real runtime limit. Modern units will shut down as soon as they detect a low oil condition as a way of protecting themselves from long can a generator run

Generator engine oil begins to degrade and runs low after approximately 150-200 hours of use.

Low oil levels and excess heat are essential considerations when running the unit beyond its rated specification.

During the initial 12-24 hour period of continuous running, the unit builds up borderline levels of heat.

Still, we think it would be best if you considered allowing a cool-down period to prevent damage. When running your generator in warmer weather, consider packing ice around it and placing a fan nearby to help cool the unit.

We can’t stress enough to you about the need for proper maintenance and heeding the manufacturer’s specifications. If you’re in a situation that demands continuous long-term use, a standby generator is a solution.

They’re capable of constant use in the 500 hours or approximately three-week range. As with any generator that’s pushing its runtime limits, excessive heat is the enemy, so always perform the recommended maintenance procedures.


As you learn more about your generator and its limitations, consider first the type of fuel it uses. Gas units are more efficient and need less fuel to produce the same amount of power as their propane counterpart. Consider also how long a generator can run continuously.

Overall, recommendations are 24 hours max runtime. Generator stress caused by excessive runtime is costly and usually unnecessary. Always follow recommended maintenance procedures to maximize the life of your generator and keep it working at its best in any environment.